This work presents a 3D interactive gaming paradigm called Cyberball3D+ for the secluded space of an fMRI scanner. The Cyberball3D+ game is a virtual ball-toss game where participant is either excluded or not from ball tossing played by three virtual players and the subject in the scanner. The game proposed was designed to render an interactive Virtual Environment (VE) on an fMRI display, enabling the conduct of formal neuroscientific experiments and investigating the effects of social exclusion, empathy and different level of anthropomorphism on human brain activity. Although this work focused on the technical implementation of the system, for the first time, we propose a validated neuroscientific fidelity metric of character believability and emotional engagement. The system was developed in close collaboration between the Technical University of Crete where the technical implementation took place and the Brighton and Sussex Medical School where the initial fMRI experiments were conducted using the system proposed. The results demonstrated that participating in a high anthropomorphism environment rather than a low anthropomorphism environment activated both frontal cortex and superior temporal gyrus. This suggests that compared to more human like avatars, playing the non-anthropomorphic avatars is less subjectively rewarding and potentially anxiogenic. In addition, the results indicated that when studying complex emotional responses, a high level of anthropomorphism of synthetic characters engages neuroscientific patterns of brain activation as in real-world circumstances. A broader aim of this work was to assess whether such powerful social-psychological studies could be usefully carried out within VEs advancing cognitive neuroscience and computer graphics research.